Responding to the increasing demand for empirical evidence of cost-effectiveness in drug abuse prevention and intervention programs, this research examines health care utilization and health care costs for drug abusers and their family members following initiation of insurance-covered treatment. We test cost-reduction hypotheses for the primary effects of treatment on patients' own subsequent health care costs, and secondary effects on the health care costs of drug-abusers' family members. Emphasizing external and ecological validity, we propose an analysis of inflation corrected measures from actual insurance claims records of a large self-insured, multisite company over a period of 1974-1987. Limitations of the quasi-experimental design are minimized by employing two complementary statistical procedures. Analysis of covariance across three control groups is used to control for (1) initial differences in pretreatment, (2) self-selection into medical treatment, (3) self-selection into drug dependence treatment, and (4) simple effects of time. Time series analysis will be used to control for the effects of maturation and history. Although the 20,000,000 records comprising this archival dataset will require considerable computer time, and personnel resources, there are substantial benefits to be gained from examining "real world" outcomes within the context of the operational environment.